1. Field of the Invention
The present invention relates to a sheet processing device for carrying out processing on sheets, and to an image forming apparatus having the sheet processing device in a main body of the apparatus and forming an image on sheets and then allowing the sheet processing device to carry out processing on the sheet. More specifically, the invention relates to a sheet processing device in which the vertical space of a sheet path is reduced and the sheet is prevented from lifting up, and to an image forming apparatus having the same.
2. Description of the Related Art
Conventionally, for example, sheet processing devices align the ends of sheets received from a main body of an image forming apparatus at an intermediate stacking station, carry out processing at a sheet processing unit where the sheets are stapled together, and discharge and stack the sheets. The intermediate stacking station includes the sheet processing unit, which corresponds to sheet processing means, intermediate rollers, and sheet-discharging rollers. The sheet processing unit is disposed upstream of the nip of the intermediate roller in the sheet conveying direction.
Therefore, in the sheet processing mode, the conventional sheet processing device reverses the sheet conveying direction to an upstream direction once the sheet has passed between the intermediate rollers until the sheet is brought into abutment with a reference wall, so that the rear ends of the sheets are aligned. Subsequently, the sheet processing device carries out processing on the sheets at the aligned position using the sheet processing unit, and discharges and finally stacks the sheets on a stacking tray using the sheet-discharging rollers.
However, in the conventional sheet processing device, since the sheet processing unit is disposed upstream of the intermediate rollers, the sheets which have passed through the intermediate rollers must be fed back in the upstream direction, and thus the device is provided with a first sheet path from the entrance of the sheet processing device to the intermediate roller, and a second sheet path from the reference wall to the discharging rollers, which are arranged on two levels, that is, one above the other. Therefore, the height of the main body of the sheet processing device is obliged to increase, and thus the size also increases.
Since a plurality of sheets are stacked when carrying out processing on the sheets, sometimes a next sheet cannot proceed onto the preceding sheet without a jam. Therefore, a holding mechanism for preventing the stacked previous sheets from lifting up is provided, and this holding mechanism also prevents the height of the main body from being reduced.